South Carolina Highway 642South Carolina Highway 642, is a state highway in the southeastern part of the U.S. state of South Carolina. It travels within the Summerville and North Charleston areas.Route descriptionSR 642 runs for from U.S. Route 17 Alternate southwest of Summerville to US 52/US 78 in North Charleston. Dorchester Road is a heavily congested highway during morning and evening traffic periods.HistoryCurrent plans call for widening of the road from Summerville to US 17 Alternate. This has been completed.Major intersections